OpenAI Codex CLI error
Codex CLI: MCP client for <server> timed out after 10 seconds
MCP client for `<server>` timed out after 10 seconds. Add or adjust `startup_timeout_sec` in your config.toml:Status: WorkaroundLast verified 2 documented fixes7 sources
What it means
The MCP server did not finish starting within its startup timeout (default 10 seconds). Builds before 0.50.0 showed this as a generic "request timed out" startup failure (#2555); PR #5595 added the clearer message so users can self-serve.
Causes
- The server takes longer than startup_timeout_sec to start (default: 10 per the official MCP docs).
- On Windows, MCP servers missed core environment variables and often failed to start without explicit per-server env blocks (PR #5579).
How to fix it
- Fix 1.
Raise the startup timeout for that server, as the message says (official MCP docs and configuration reference).
TOML[mcp_servers.context7] startup_timeout_sec = 30 - Fix 2.
Upgrade: 0.31.0 improved MCP initialization error handling (PR #3243, which references #2555), 0.50.0 added the explicit timeout message (PR #5595), and 0.51.0 passes core env vars to Windows MCP servers (PR #5579).
More Codex CLI errors
All 14 Codex CLI errorsstream disconnected before completion: stream closed before response.completedStatus: Workaroundstream disconnected before completion: error sending request for url (https://chatgpt.com/backend-api/codex/responses)Status: OpenError running remote compact task: stream disconnected before completion: error sending request for url (https://chatgpt.com/backend-api/codex/responses/compact)Status: Fixed in releaseSelected model is at capacity. Please try a different model.Status: By designYour access token could not be refreshed because your refresh token was already used. Please log out and sign in again.Status: Fixed in releaseCodex ran out of room in the model's context window. Start a new thread or clear earlier history before retrying.Status: Fixed in releaseError logging in: Port 127.0.0.1:1455 is already in useStatus: WorkaroundToken exchange failed: token endpoint returned status 403 ForbiddenStatus: Workaround
Related reading
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- Codex and Claude Code in July 2026: Agent Controls Are the FeatureCodex and Claude Code July 2026 updates compared: why approval modes, resumable work, MCP auth, artifacts and review surfaces now matter as much as models.
- AgentCanvas is a visual adapter for Claude Code and CodexAgentCanvas is a visual adapter for Claude Code and Codex that puts artifacts, decisions and handoffs on one board, so the next agent or human can see them.
- GitHub Copilot Agent Finder: What ARD Means for Third-Party AI Tools in 2026GitHub Copilot Agent Finder discovers and invokes MCP servers, skills and agents like Claude and Codex. How the open ARD spec changes AI tool integration.
- AgentMemory Is Useful Only If You Audit What It RemembersAgentMemory gives Claude Code, Codex and Cursor persistent local memory. The real adoption test is whether your team can inspect, prune and govern it.
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FAQ
What does "MCP client for <server> timed out after 10 seconds" mean in Codex CLI?
The MCP server did not finish starting within its startup timeout (default 10 seconds). Builds before 0.50.0 showed this as a generic "request timed out" startup failure (#2555); PR #5595 added the clearer message so users can self-serve.
How do I fix "MCP client for <server> timed out after 10 seconds"?
There are 2 documented fixes. Start with the first: Raise the startup timeout for that server, as the message says (official MCP docs and configuration reference).
Is this Codex CLI error fixed?
Status: Workaround. No release removes the cause. The documented fixes work around it. Affected versions: Reported on codex-cli 0.23.0 to 0.31.0 on Windows 11 (#2555)
Sources
Last verified against 7 sources: official docs, maintainer replies and release notes.
- github.comhttps://github.com/openai/codex/issues/2555
- github.comhttps://github.com/openai/codex/pull/3243
- github.comhttps://github.com/openai/codex/pull/5595
- github.comhttps://github.com/openai/codex/pull/5579
- github.comhttps://github.com/openai/codex/releases/tag/rust-v0.50.0
- learn.chatgpt.comhttps://learn.chatgpt.com/docs/extend/mcp
- github.comhttps://github.com/openai/codex/blob/ce0323f2f2d3b25e82806cd555237da3db4e1897/codex-rs/codex-mcp/src/connection_manager/startup.rs
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